A passenger puts his luggage in the overhead bin on an American Airlines flight out of John F. Kennedy Airport in Jamaica, New York.

Robert NickelsbergGetty Images

Airlines started charging fees for checked bags a few years ago. Now passengers are testing the limits of what they can carry onto planes. Some flight attendants say it's getting out of hand. But airlines are trying to address the problem with bigger overhead bins.

Sisters Molly and Jess Nelson are scheming with their parents, Sue and Scott, about what to cram into a big black suitcase. It's the only bag the family will pay for between the four of them on their trip from Minneapolis to San Diego.

"Well, I was thinking we could share one of those backpacks because it's pretty big," Jess says. But Molly isn't so sure about that plan. "I packed a lot, though, so I'm going to need my own bag," she says.

Besides the shared bag, they will each bring carry-ons. And they have a special trick: they use duffel bags that don't have hard spines. Jess says they're malleable enough to squeeze into overhead bins — more or less.

"I feel like it's right on the edge of fitting as a carry-on," Jess says. "When I'm stuffing it up there, I always feel like people are like, 'That shouldn't be here. It's too big.' "

Airlines introduced checked-bag fees in 2008, when fuel prices were hammering them. Southwest doesn't charge for the first two checked bags, but most others do — usually about $25 for the first bag and $35 for the second.

That has prompted many travelers like the Nelsons to devise clever ways of using only carry-ons. Some try to get their overly large carry-ons through security and keep their fingers crossed that they'll get to check the bags at the gate without a fee.

Linda Verboom, a flight attendant based in Washington, D.C., says one strategy can leave a passenger looking like the Michelin Man. She has seen passengers wear tons of layers so that they don't draw scrutiny with bulky carry-ons.

"I did have a young girl come on recently that was wearing a pair of leggings, a pair of shorts and a skirt, several T-shirts, and one of those zip-up hoodies to try to get as much on board as she possibly could and later started to undress and to roll everything up and put it into her suitcase," Verboom says.

Verboom says messing around with carry-ons can delay departures and distract flight attendants when they're supposed to be looking out for suspicious activity.

"There's a long list of things we're supposed to be watching out for during boarding," Verboom says. "Few of those things can be accomplished when you're in the middle of the aisle wrestling a bag in or out of an overhead bin."

The union she belongs to, the Association of Flight Attendants, made that argument in a hearing Tuesday held by the Senate Appropriations Subcommittee on Homeland Security.

The union says the Transportation Security Administration should take over the job of enforcing a one carry-on, one personal item limit. That's already the rule, but the flight attendants say airlines don't enforce it uniformly. In addition, while most airlines require carry-on bags to be about 45 inches of combined height, width and length, they can ask the Federal Aviation Administration to allow bigger dimensions. The group says that would help curb the "carry-on chaos" flight attendants have to deal with.

But airlines are taking their own steps to deal with carry-on issues. Gate agents are looking out for bags that are too big. And some airlines, like American, United, Delta and US Airways, are expanding the size of their overhead bins.

Some travelers may wonder, why not just incorporate the cost of checked bags into the ticket price and not charge the extra fees?

"It would be much simpler if it were that way," says Tim Smith, a spokesman for American Airlines. Smith says if his airline did that, it would look a lot more expensive than other carriers on fare comparison sites. That could be deadly.

"Experience has shown us that shoppers will walk across the street for as little as a dollar or two difference," Smith says.

And he says some people prefer the a la carte pricing where they only pay for checked bags if they need them. On the whole, fliers actually do have a lot of ways to dodge bag fees. Some elite flier and credit card programs waive them.

Smith says only about 25 percent of passengers actually pay the bag fees. But airlines probably don't want to part with the fees they do collect.

Henry Harteveldt, an airline and travel analyst at Atmosphere Research Group, says that last year, the airline industry's profit margin was only 0.3 percent, and probably would've been worse without baggage fee revenues. That makes the use of bag fees crucial.

"From a PR standpoint, it's probably one of the blackest eyes the airlines have ever earned," Harteveldt says. "But from a business standpoint, it's a smart move."

In other words, don't expect bag fees to go away any time soon.

Copyright 2012 National Public Radio. To see more, visit http://www.npr.org/.

Transcript

DAVID GREENE, HOST:

Many airlines passengers thought it was outrageous when they had to start paying to check luggage a few years ago. To avoid the fees, some passengers began experimenting to see just how big a piece of luggage they could get onto the airplane with them. Some flight attendants say that's getting out of hand and so airlines are now trying to address the problem with bigger overhead bins.

NPR's Annie Baxter has that story.

ANNIE BAXTER, BYLINE: Tell me if you've ever had a conversation like this. It's the night before a big trip and you're trying to figure out how to avoid checking bags and paying a bunch of fees.

JESS NELSON: Well, I was thinking that we could share one of those backpacks because it's pretty big.

MOLLY NELSON: I packed a lot though.

(SOUNDBITE OF LAUGHTER)

NELSON: So I'm going to need like my own bag.

BAXTER: These two sisters, Molly and Jess Nelson, are scheming with their parents, Sue and Scott, about what to cram into a big black suitcase. It's the only bag they'll pay for between the four of them on their trip from Minneapolis to San Diego.

SCOTT NELSON: This is the one we will check.

(SOUNDBITE OF ZIPPER)

BAXTER: Besides that, they'll each bring carry-ons. And they have a special trick: they use duffel bags that don't have hard spines. Jess says they're malleable enough to squeeze into overhead bins – for the most part.

NELSON: I feel like it's right on the edge of fitting as a carry-on. When I'm like stuffing it up there, I always feel like people are, like, that shouldn't be here.

(SOUNDBITE OF LAUGHTER)

NELSON: You know, like it's too big.

BAXTER: Airlines introduced checked-bag fees in 2008, when fuel prices were hammering them. Southwest doesn't charge for the first two checked bags, but most others do - about 25 bucks for the first bag and 35 for the second.

That's prompted lots of travelers like the Nelsons to devise clever ways of using only carry-ons.

Linda Verboom, a flight attendant based in Washington, D.C., says one strategy leaves some flyers looking like the Michelin Man. She's seen passengers wear tons of layers so that they don't draw scrutiny with bulky carry-ons.

LINDA VERBOOM: I did have a young girl come on recently that was wearing a pair of leggings, a pair of shorts and a skirt, several T-shirts, one of those zip-up hoodies, to try to get as much onboard as she possibly could and later started to undress and, you know, roll everything up and put it back into her suitcase.

BAXTER: Verboom says messing around with carry-ons can delay departures and distract flight attendants when they're supposed to be looking out for suspicious activity.

VERBOOM: There's a long list of things that we are supposed to be watching out for during boarding. Few of those things can be accomplished when you're in the middle of the aisle, you know, wrestling a bag into an overhead bin.

BAXTER: The union she belongs to, the Association of Flight Attendants, made that argument in a Senate subcommittee hearing yesterday.

The union wants the Transportation Security Administration to take over enforcement of the number of carry-on bags and their size. The group says that would help cut down on the carry-on chaos that flight attendants have to deal with.

But airlines are taking their own steps to deal with carry-on issues. Their gate agents are looking out for bags that are too big. And some, like American, United, Delta and US Airways, are expanding the size of their overhead bins.

Travelers may wonder, why not just incorporate the cost of checked bags into the ticket price and not charge the extra fees?

TIM SMITH: It would be much simpler if it were that way.

BAXTER: Tim Smith, a spokesman for American Airlines, says if they did that at his carrier, the airline would look a lot more expensive than other carriers on fare comparison sites. That could be deadly.

SMITH: Experience has shown us that shoppers will walk across the street for as little as a dollar or two difference.

BAXTER: On the whole, fliers actually do have a lot of ways to dodge bag fees. Some elite flier and credit card programs waive them. But whatever airlines can pull in through bag fees, they're unlikely to give up, especially given how tough it's been for the industry to turn a profit.